Use seleniums BrowserLocator interface to figure out where the browsers are installed. This should make test-helper much more friendly to Windows and MacOS.
Print those stupidly implemented InitializationError completely, so we actually know what caused them to be thrown in the first place.
fixed deadlock when one browser would fail to start.
Don't attempt to start browsers and HTTP server multiple times if it failed before.
Merge remote-tracking branch 'st-js/master'